1. Field of the Invention
The present invention relates to a method and an apparatus each for inspecting an appearance of an article through a photographed image of a surface thereof.
2. Description of the Related Art
As a method for inspecting the state of a surface of an article, various methods are generally known, and a method is employed, in particular, which inspects the state of the surface of the article by photographing the article with a CCD camera and processing its image. In this case, for example, pixels at about ten points are selected from among pixels showing a surface to be inspected in the image photographed with the CCD camera, and a mean value of brightnesses of the pixels is set as a standard value, so that the brightness of a pixel at a point to be measured is compared to the standard value, thereby inspecting the state of the surface of the article.
However, such a conventional inspection method has a problem that inspection results do not stable because of changes in the surface state of the article, changes in the external environment such as sunlight, room light or the like, the presence or absence of illumination for photographing the image and so on. Further, elimination of the influence of the external environment to stable the inspection results requires a large investment.